Updated 19th February 1999; 12th May, 12th November 2002; 4th, 26th November 2003; 18th January 2004; 30th October 2007; 7th January 2008; 5th January, 5th November 2011; 18th February, 19th September 2012; 4th December 2015; 29th April, 30th June 2018
A complicated cave of great variety. The entrance "amphitheatre" has a number of small caves at the back, at least one of which provides a straight 30m drop to the main tunnel. The main entrance is a large, sloppy, leafy slope down into a sloping chamber that provides the focus to the cave. The first (and much small second) slope exits on the right provides access to a long series of phreatic domes, Tree Gallery. The apparent end is bypassed by a squeeze at roof level possibly reached up a 7m long tree trunk. Further squeezes lead to a continuation of the domes, a division of the ways and two chokes.
Just back from the junction a rift descends to a three ways junction, one passage containing a long pool. At the far end of the entrance chamber a rift on a rock slope provides entry to Nuts Passage, a series of tubes and phreatic chambers.
The main way on is down through a squeeze on the left of the entrance chamber. Large phreatic chambers soon close down to the right and straight ahead, while to the left a 5m climb leads to the head of a 20m pitch. At the base of the pitch is the complicated Mini Maze, the route on being a tight squeeze to walking passage which runs to the top of a 17m pitch. This drops straight into the vadose section of the cave. Upstream leads to a 4m climb and drop down over a barrier. The next obstacle is a 16m high climb over greasy calcite where, near the top, pitons are useful. A 12m pitch back to the stream follows immediately. The passage then continues for 200m to a tortuous route in rotten rock until it becomes too tight.
Downstream the cave passes the odd obstacle in a mainly narrow streamway to end after a couple of hundred metres at a calcite choke. The stream is thought to resurge in the Hoyo Mortiro on the east side. Another resurgence on the west of the depression has an unknown source but could come from Torca CEZ. A water trace from the end of the Orillón system in November / December 2015 showed a strong positive at the Esquileña resurgence near Riva. Weakly positive results were seen on detectors left in the eastern resurgence in the Hoyo Mortiro. Full details of this trace can be found on the Orillónzuco site.
Several flints were found by C.A.E.A.P. in 1989 in the rock shelters around the entrance, and fragments of human skull on the entrance slope. A photo of the medieval vase is to be found in Ruiz Cobo Jesús and Smith Peter, 2003, page 41.
The cave has been extended by the AEC Lobetum, adding about 730m to the length.
The San Mateo series off Tree Gallery is shown
Valero Enrique y Soriano Ángel, 2007 has the length as 3200m and a depth of 75m. The same publication also has an area map showing the following sites: Rio Seco, Cueva Brazada, Torca de Blas, Cueva de La Pila, Cueva de Coquisera and Cueva del Coverón.
Additional length was added during the AEC Lobetum September 2012 visit - another 350m upstream. This extension starts before the original upstream end and bypasses the "too tight" section. There is then another 200m of streamway which ends at high avens which bring in water. These are apparently close to Torca XLs which has a cobble dig at it's base. There is possibly about 100m height difference between this dig and the floor of the avens.
With the 2009 discovery of Torca CEZ by the AEC Lobetum, lower down in the Hoya de Mortiro, a new system looks to be close to linking with Coverón. A trip by Matienzo cavers in January 2012 (by invitation) went to a couple of ends and there are various leads apparently still open, including at least one draughting dig. Both Coverón and CEZ should be resurveyed. A partial resurvey of Coverón was carried out in August 2012 (batch 0002-12-01.svx) which put the nearest point to CEZ at an altitude of 225m, possibly 20m above (inaccurately surveyed) CEZ and about 40m distant.
Over Easter 2018, the Matienzo Karst Entomology Project (led by Tom Thompson) followed up previous work by collecting bugs, spot sampling and setting pitfall traps in a number of sites under a Cantabria-wide permit. The Entomology Project carried out some work in this cave.
References: Fernández Gutiérrez et al, 1966;
anon., 1975b (logbook); Kendal Caving Club and Manchester University
Speleological Society, 1975 (survey
and photo); anon., 1975a; Manchester University Speleological Society, 1982
(survey); Mills L D J, 1981; Mills L D J and Waltham A C, 1981 (survey);
Corrin J S and Smith P, 1981; material in file; anon., 1988 (logbook); anon.,
1993a (survey); Corrin J, 1994b
(survey); García José León, 1997 (survey); Corrin Juan,
1997c; anon., 2000e; Ruiz Cobo Jesús and Smith Peter, 2003; Valero
Enrique y Soriano Ángel, 2007 (survey); León García José, 2010 (survey and photos); anon., 2012a (January, February logbook); anon., 2012d (summer logbook); Papard Philip, Corrin Juan and Smith Peter, 2014; anon., 2018b (Easter logbook)
Entrance pictures : 2002 & 2008 : Spanish team (2009) on Facebook : Easter 2018
Underground picture(s): Entrance slope and Tree Gallery 2008 : Spanish team (2009) on Facebook : Easter 2018
Detailed Survey : 1975 high res 1975 low res Tree Gallery extension
Tree Gallery extension - San Mateo (anon., 1993a; AEC Lobetum) high res low res
Line Survey: coordinates taken from paper survey (z-coords will be way out)
On area survey : line survey with partial Torca CEZ line survey
Survex file : partial Coverón survey with partial (inaccurate) CEZ survey (2012 - Amended magnetic declination December 2013 to align with Eur79 grid) :
Off drawn survey with approximate z - Amended magnetic declination December 2013 to align with Eur79 grid and and coordinates altered to fit ETRS89 datum, April 2014.
With CEZ, Orillón and Mortiro-Esquilón
Passage direction rose diagram: generated 30/6/2018